Elastomeric Harnesses Decrease Aerosol Particles Leak and Improve the Fit of Surgical Masks

Abstract

Importance. The outbreak of Coronavirus diseases 2019 (COVID-19) disease has increased demand for N95 respirators, surgical masks, and other facial coverings in an effort to stop the spread of SARS-CoV-2. Research shows that N95 respirators perform the best at filtering viral droplets and aerosols, however these masks are much more difficult to manufacture and expensive to distribute on a large scale, which led to shortages during the early phases of the pandemic. Surgical masks, on the other hand, were more widely available and have been previously used to mitigate the spread of tuberculosis and influenza. However, surgical masks are not designed to filter aerosols because unlike the N95, they do not fit tightly around the nose and mouth, and often have reduced filtration efficiency. Objectives. To evaluate the filter filtration efficiency (FFE) of three elastomeric face harness designs in hospital and research settings in order to improve facemask seal and preserve comfort. Design, setting and participants. A multi-institutional collaboration between engineers and health professionals, conducted between November 2020 and March 2021, was set up to design an elastomeric harness to improve the face seal of a surgical mask. Three elastomeric harness designs were created with harness designs 1 and 2 tested in a research laboratory setting and harness design 2.1 tested in a hospital setting. The harness can be manufactured from a single sheet of elastomer and can be used with a surgical mask to provide a low-cost, easy-to-manufacture, reusable alternative to an N95 respirator. The initial harness design 1 was laser cut for testing and design 2 was developed to improve the detected particle leakage around the nose bridge area by introducing more material in that region. The extra material is looped multiple times and secured, forming a more secure seal between the nose and the surgical mask. Due to expressed discomfort levels and vision disruption, harness design 2.1 is developed for hospital settings with shorter looping material around the nose bridge. The designs were tested on mannequins and human volunteers using IR imaging and standard fit testing equipment to help optimize face seal and comfort. Main Outcomes and Measures. Our elastomeric harness can improve the seal of a surgical mask allowing it to pass the fit test used to evaluate N95 respirators. When tested with human volunteers we find that all participants fitted with an elastomeric harness increase their scores on the NIOSH fit test used to evaluate N95 aerosol filtration efficiency. Of this group, 24/39 participants achieved a passing score of 100 or more while wearing the second harness design. By studying the location of air leakage using IR imaging we were able to determine the nose bridge region of the masks is most prone to leakage when using our first elastomeric harness. Further optimization of the harness may increase the percentage of those who pass the NIOSH fitness test. Conclusions and Relevance. Overall, these results confirm that elastomeric harnesses combined with surgical masks improve their ability to filter aerosolized particles, which is especially important when in close proximity to individuals who are infectious or while performing aerosol-generating medical procedures.